This invention relates to a bidirectional add/drop amplifier module, more specifically, to the bidirectional add/drop amplifier module that is simply constructed using a single bidirectional multiplexer such as an arrayed-waveguide grating.
This invention may be more clearly understood by referring to the cited papers, as follows:
F. Elrefaie, "Multiwavelength survivable ring network architectures", International Conference on Communication, 1993, paper 48.7; F. Shehadeh, R. S. Vodhanel, M. Krain, C. Gibbons, R. E. Wagner, and M. Ali, "Gain-equalized, eight-wavelength WDM optical add-drop multiplexer with an 8-dB dynamic range", IEEE Photonics Technol. Lett., vol. 7, no. 9, pp. 1075-1077, September, 1995; K. P. Ho, S. K. Liaw , and C. Lin, "Performance of an eight-wavelength bidirectional WDM add/drop multiplexer with 80-Gbit/s capacity", Optical Fiber Communication '97, paper TuR1; J. L. Gimlett, and N. K. Cheung, "Effects of phase-to-intensity noise conversion by multiple reflections on gigabit-per-second DFB laser transmission systems", J. Lightwave Technol., vol. 7, no. 6, pp. 888-895, June, 1989; N. Henmi, Y. Aoki, S. Fujita, Y. Sunohara, and M. Shikada, "Rayleigh scattering influence on performance of 10 Gb/s optical receiver with Er-doped optical fiber preamplifier," IEEE Photonics Technol. Lett., vol. 2, no. 4, pp. 277-278, April, 1990; C. Barnard, J. Chrostowski, and M. Kavehrad, "Bidirectional fiber amplifiers," IEEE Photonics Technol. Lett., vol. 4, no. 8, pp. 911-913, August, 1992; K. Kannan, and S. Frisken, "Unrepeatered bidirectional transmission system overa single fiber using optical fiber amplifiers," IEEE Photonics Technol. Lett., vol. 5, no. 1, pp. 76-79, January, 1993; W. Y. Guo, and Y. K. Chen, "High-speed bidirectional four-channel optical FDM-NCFSK transmission using an Er.sup.3+ -doped fiber amplifier," IEEE Photonics Technol. Lett., vol. 5, no. 2, pp. 232-235, February, 1993; Y. H. Cheng, N. Kagi, A. Oyobe, and K. Nakamura, "622 Mb/s, 144 km transmission using a bidirectional fiber amplifier repeater," IEEE Photonics Technol. Lett., vol. 5, no. 3, pp. 356-358, March, 1993; R. J. Orazi, and M. N. McLandrich, "Bidirectional transmission at 1.55 microns using fused fiber narrow channel wavelength division multiplexers and erbium-doped fiber amplifier," IEEE Photonics Technol. Lett., vol. 6, no. 4, pp. 571-574, April, 1994; M. O. van Deventer, and O. J. Koning, "Unimpaired transmission through a bidirectional erbium-doped fiber amplifier near lasing threshold," IEEE Photonics Technol. Lett., vol. 7, no. 9, pp. 1078-1080, September, 1995M.; O. van Deventer, and O. J. Koning, "Bidirectional transmission using an erbium-doped fiber amplifier without optical isolators," IEEE Photonics Technol. Lett., vol. 7, no. 11, pp. 1372-1374, November, 1995.
A wavelength division multiplexing (WDM) optical network uses different wavelengths to transmit a plurality of optical signals unconcernedly with any transmission mode and speed, whereby a super highway and wide area network can be realized. The network requires a drop function for receiving a wanted signal at each node and an add function for transmitting a wanted signal at each node. Therefore, a WDM add/drop multiplexer is an important constituent for constructing the WDM optical network. The add/drop multiplexer is especially emphasized in a WDM ring network.
In order to a bidirectional ring network using a unidirectional WDM add/drop multiplexer, at least two pairs of optical fiber are required. A bidirectional WDM add/drop multiplexer that can not only transmit but also add/drop a signal in bidirection is significantly reduce consumption of the optical fiber required in constructing the bidirectional ring network.
Such bidirectional WDM add/drop multiplexers are proposed in U.S. Pat. No. 5,548,438 issued Apr. 20, 1996 and entitled "Bidirectional optical amplifier", U.S. Pat. No. 5,633,741 issued May 27, 1997 and entitled "Multichannel optical fiber communications", and a paper of K. P. Ho, et al., "Performance of an eight-wavelength bidirectional WDM add/drop multiplexer with 80-Gbit capacity", Proceeding of Optical Fiber Communication, 1997.
These bidirectional WDM add/drop multiplexers, however, use a 1.times.N demultiplexer and an N.times.1 multiplexer, whereby their structures are very complicated and the manufacturing cost is very high.